>>940251 Do on my own >>940256 I have gyro sensors on my other hand so i only need to get the rotation it gives to a variable and the motor rotation in another variable. The motor rotation is the difference between the variables
Anyone know what the ratheon sarcos exoskeleton used for sensors? They used servo motors and were made back around 2007. With the advances in MCUs hobbyists should be able to build something similar now.
Looking at it I'm pretty confident I could build something similar, some modern MCUs could probably command every servo motor in the entire skeleton. But the control mechanism is a complete mystery, is it using pressure sensors in every joint, or is it just sensors in critical points with some sort of IK system moving the others.
>>940385 >>hydraulics are shit. Sure they are torquey, but they are less efficient, less responsive, and require more maintenance than electric actuators.
Using variable vane impellers for the limbs is a bit odd, especially if you really mean variable vane impeller and not variable displacement hydraulic motor. For one it makes things really complicated and less compact. Impellers do not work well at low speeds and are really more of high speed low torque devices.
The propane engine driving everything has some problems. For one, you waste power if you aren't doing much of anything. When you move a bunch of limbs at once the engine can struggle to keep up, which is one of the problems Boston Dynamic's ATLAS robots had in the DARPA challenge.
But hey, that's just like your opinion man.
Now in my opinion the best way to build a DIY exoskeleton would be to use water-cooled brushless motors driven by capacitors. This is what SCHAFT used to dominate the first DRC. You can buy water cooled brushless motors that have similar specs to what SCHAFT used from china for cheap. For capacitors, EV regenerative braking capacitors might work and are cheap. Only difficult part would be getting the damn harmonic drives.
Here's more on the actuators SCHAFT used. http://web.tuat.ac.jp/~venture/ronbun/ReadingGroupControl/2010_Design_for_high_speed_and_torque_leg_with_coolant.pdf
>>940580 >>They used servo motors nope they used hydraulics.
>>some modern MCUs could probably command every servo motor in the entire skeleton. computation is cheap, sadly actuators are not(well yet at least)
>>is it using pressure sensors in every joint, or is it just sensors in critical points with some sort of IK system moving the others. We don't really know. We do know the operator holds onto something that measures force on it(pic related). So it probably does something like the IK system you described, probably moving to decrease force applied by the operator. Although they probably use pressure sensors too.
Sarcos has a humanoid robot that has force sensors on every joint, so it would not be surprising that their exoskeleton does the same: http://www.cs.cmu.edu/~bstephe1/papers/humanoids10.pdf
>>940586 Everywhere says the XOS 2 uses servo motors with an IC powerpack. Maybe the XOS-1 was hydraulic. The hydraulic ones always look slow and unresponsive.
Actually I found a way to make cheap actuators, there's a bunch of direct drive 3 phase BLDC motors that can be turned into high powered servos with an encoder, I already have a motor and servo controller with a canbus I'm in the process of modifying it for high voltage for another project but it should be able to let you have 500w- 1kw servos per joint.
>especially if you really mean variable vane impeller and not variable displacement hydraulic motor
Just looked it up, this is what I was imagining. I've worked with boat hydraulics before but I don't know a whole lot about them, didn't even know there was such a thing.
The only reason I said propane was so it would be safer to used in enclosed spaces, and it's a bit easier to just fill up a fuel tank than to wait for batteries to recharge.
Looking up ATLAS now, didn't know it had been tried already. Thanks for that.
I didn't realize that capacitors had advanced enough to be used for something like this. Pretty freaking cool.
I guess I just hate the thought of being dependent on batteries. It seems like every day I read about a new battery technology that promises greater density, service life, etc. but nothing ever changes.
Probably is the best bet though. What I do know is that hydraulic tanks can get pretty fucking hot and I can't imagine lugging that around in a suit all day.
>>941004 I wonder how much torque you need for a exoskeleton with performance like the XOS.
You can get these hoverboard and self balancing vehicle BLDC motors for next to nothing, even RC hobby engines cost 4x as much as them.
With no cooling and their stock limits I think they're around 20nm at stall. But with water cooling combined with the high voltage and high current motor control I'm building you might be able to get 100nm? I need to find out how roughly many nm the largest muscles in human limbs generate.
>>941100 yikes! The wiring on that hoverboard motor looks nasty.
>>water cooling The reason SCHAFT was able to cool their motors was because all the windings on said motors were in direct contact with the motor case. (pic related)
Those hoverboard motors would be very difficult to water cool. I don't even know how you'd get tubing in there.
>> I need to find out how roughly many nm the largest muscles in human limbs generate. for an exoskeleton it is more important to have actuators with a large torque density, that is the ratio or torque to weight. If your actuators are putting all their torque just into lifting their own weight they are sort of useless.
Let's compare the torque density of a standard servo to this hoverboard motor.
for servo From here: https://www.adafruit.com/product/155 weight is 39 grams-f torque is 6.5 kgf *cm so torque to weight is 1.67 m
For the hoverboard motor from here: http://www.amazon.com/Replacement-Hoverboard-Balancing-Electric-Unicycle/dp/B017LG2D32 torque is 100 N*m using weight of 3kgf
torque to weight is 0.68 m
So not as great as our servo. However, we can get a pretty good torque to weight ratio just by gearing it down 1:5 or so, no modifications to the motor.
Are you sure hoverboard motors really have that much stall torque?
Unless you spend excessive amounts of time, you will find your exo exhausting or chafing. A robot arm is easy enough because there's no delay or error between parts. Combining a human arm with a robot arm will result in deviation which will result in wear issues.
>>941135 >Are you sure hoverboard motors really have that much stall torque? This 3kg BLDC has 60nm but it's designed for high RPM not low speed torque. http://www.jobymotors.com/public/views/pages/products.php
The funny thing about the Chinese direct drive hub motors is they mainly use them because they're too cheap to spend money on reduction gears. So they build them with maximum torque in mind, that's why it has a huge stator and copper sticking out everywhere. All they care about is having a stator with a high saturation limit and cramming as much copper as possible in.
The other thing is with cooling, the wires can actually take quite high temperatures, you just need to keep the heat away from the magnets which fail at around 90C
Switched reluctance motors might also be interesting for exoskeletons, they perform like BLDC but have no permanent magnets and will take as much current you can send without melting copper wires while stalled.
>>941230 You can get geared bike motors from china for $50. All you would have to do is change the gear ratio, add an encoder and put it in a more suitable housing. http://lipeng.en.alibaba.com/product/60201405095-800135717/hot_sale_geared_24v_dc_motors.html
>>941739 I'm making a high powered version of this. http://vedder.se/2015/01/vesc-open-source-esc/
The software is already really good, sensored and sensorless FoC, automatic configuration for almost any BLDC, supports encoders, has canbus integrated and many other useful things.
The weak part is the hardware, it was built around a TI8302 mosfet driver which has many other functions built in, it's limited to 60v and prone to be destroyed as it's powered straight from the high voltage motor input. It's also very compact but it ends up being a problem for many applications.
So I have built a board that shares much of the same layout around the MCU but completely replaced the mosfet driver and half bridge section, in theory it should be able to scale to 500 volts, and large motors without any software modifications.
Hopefully if it goes well I can sell a range of boards using the software platform, ranging from RC, drones and robots to electric motorcycles and cars.
You could mount some surface electrodes over your leg muscles. Differental emg signal is easy to amplify. You can use some instrumental amplifier ICs, like INA128. Amplified signal requires filtering to pass 20Hz to about 200 Hz (or more, but less than 500Hz).if you're going to use microcontroler boards with 0-5V adc you need to rectify signal first. Google precision full-wave rectifier design from texas instruments. To make signal scalable it's good to smooth it with lowpass filter (my best try was at 0,7-1Hz. You can easily set duty cycle of pwm with this shape of signal. Every user has different muscle signal chracteristics, so you need to calibrate you device for every muscle i believe. You have gyros plus emg signals, so i think it's posible to write neural algorythm for controling some motors with gyro feedback. I'd consider mechanical design first. You could make simple computrer model to simulate your skeleton control with yor emg plus gyroscope signals (for example export solidworks assemblies to simscape ). Some ai (based on simple neural network) could learn correct motion response. I'd design exoskeleton control thxat way.
>>944214 They might have some information on building a suit somewhere. Maybe a blog or forum. We get threads like this from time to time but wouldn't it be neat if some /diy/nasaurs actually went and built a suit? I don't know what it would be used for but it would certainly be cool.
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